1. Field of the Invention
The present invention relates to an improved flexible ski boot, or a similar type sport boot having a hard shell and soft inner liner, which allows for the boot to be flexed by the wearer by applying forward pressure via the lower leg to boot. When the boot is flexed and relaxed, a relatively constant pressure is applied by the boot to the lower leg of the wearer. The invention provides a strap, at least a part of which is elastic. The strap secures the boot to the lower leg of the wearer and may be attached to the boot or be separate from the boot. The sport boot, in addition to being a ski boot, can be for example, a hard shell boot used for roller or ice skates, a hard shell snowboard boot or a combination of a high back snowboard binding and soft snowboard boot.
2. Background of the Invention
During skiing the sole of the ski boot is rigidly connected to the ski by a ski binding. As a result, the ski boot acts as an interface between the ski and the lower leg of the skier. In order for the reaction of the ski on the surface of the snow to be transmitted immediately and accurately to the lower leg, and conversely, for the control exerted by the skier on the ski via the lower leg and the interface also to be transmitted immediately and accurately, the foot and lower leg must be held perfectly snug by the boot.
The ideal case would be for the boot to be integral with the foot and the lower leg. The portion of the boot surrounding the lower leg would then have to satisfy two incompatible requirements. On one hand, this portion of the boot would be extremely stiff so as to transmit as well as possible the forces exerted by the leg to the ski, and vice versa. On the other hand, the boot has to have sufficient flexibility for the boot to be opened, in order boot to be put on and taken off. Modern ski technique also requires that the wearer be able to feel the flexing of the boot. Various compromise solutions to this problem have been proposed to satisfy these two conflicting requirements. Most notably, high performance ski boots are provided with a non-elastic "power strap" which secures the boot to the lower leg of the wearer by use of a conventional Velcro (registered trademark) closure. Such strap is shown in U.S. Pat. No. 5,718,067. Conventional power straps tend to loosen during skiing after the initial tightening of the closure thereby becoming less effective.
Modern skiing and especially ski racing requires the skier to have excellent fore/aft balance during the turning of the ski. The construction of the ski boot plays a key role in allowing the skier or ski racer to maintain such balance. Forward pressure is applied to the front of the ski through the ski boot and bends the front of the ski more than the back. In high performance skiing or ski racing it is important that forward pressure be applied at the beginning of the turn. The turn finishes with neutral or aft pressure. Then the next turn is begun during which forward pressure is again applied to the front of the ski, and so on. All pressure is applied through the ski boot by the fore/aft movement of the skier's tibia against the ski boot. It is highly critical that the changes in fore/aft pressure be applied in a precise manner and thus any play in the fit of the ski boot in the area where the tibia meets the ski boot can cause a critical delay and subsequent loss of the skiers fore/aft balance.
Modern ski boots all include a soft, compressible inner boot liner enclosed in a hard outer shell. The conventional power strap tightens the upper cuff portion of the hard outer shell against the soft inner boot liner and the tibia of the wearer of the boot. When the ski boot is first put on the skier tightens and secures the power strap so that it puts pressure on the inner liner and compress it. Power straps adjusted to a fixed length tend to loosen during repetitive ski turns because the constant changing between forward and neutral or aft pressure tends to further compress the inner boot or loosen the Velcro fastener. If the power strap is loosened the skier no longer feels a constant pressure on the tibia and thus partially loses the feeling for the snow during critical portions of the turn. The instant invention enables the ski boot to apply a constant pressure to the tibia portion of the lower leg of the wearer throughout the turn even if the compression of the inner liner is increased, or the Velcro or similar type fastener loosens, after the boots are secured to the wearers feet and numerous linked skiing turns are completed.
Since human anatomy is vastly different from one individual to another it is unlikely the wearer will get a good boot fit, and therefore poor skiing characteristics of the boot will result, as the best fit gets the best response. In particular it is the voids and hollows that allow the leg or foot to move with respect to the boot i.e. boot slop. These voids and hollows create dead spots so when the skier exerts his or her muscles in attempts to articulate their joints there is no response from the ski. Also the harder shell even covered with foam on the inside may create pressure points which irritate the skier and lead to foot pain. It is also the nature of the construction of modern ski boots that tightening one part of the boot affects the fit and performance characteristics of the other section and the overall boot.
In the act of skiing it is the ski reacting to the skiers movements that determines the direction of travel of the ski-skier system. In this scenario it is the ski boot that transmits to the ski the muscle movements of the skier as forces, moments and couples. Specific to this invention it is the lever action of the upper cuff of the ski boot moving elastically in a forward direction that adds or redistributes a load to the front of the ski and integrated with other elements of skiing causes the ski to take a curved path and thereby allowing the skier to negotiate turns going down the hill. This loading of the ski tip elastically through the ski boot coupled with the forward movement lower leg is what, at least in part, allows the skier to stay in balance and to control the radius or tightness of the turn.
For a ski to operate as designed it needs, along with other elements of skiing, forward pressure applied to it by the skier through the upper cuff of the ski boot. This is accomplished by the skier using the upper cuff as a lever in the fore-aft direction, pushing the shaft of his leg forward against the front of the boot thereby applying pressure to the front of the ski. The control of this pressure with respect to the movement of the shaft of the leg is critical to the control of the turn. Ski boots as designed with a fixed geometry and elasticity will allow this to happen if the ski boot is perfectly fitting and the elasticity of the boot is exactly matched to the weight of the skier.
With any given geometry and elasticity of a ski boot a certain amount pressure on the front of the ski boot will allow a certain amount of deformation of the boot and will apply a certain amount of load to the ski tip. This must be done systematically throughout the turn for the skier to stay in balance. The application of pressure is therefore time sensitive. In present day ski boots as stated above there are voids and hollows and they can occur in the upper cuff area as well as anywhere in the boot. This invention eliminates this problem by bonding the lower leg to the upper cuff or what is known as the rear spoiler of the ski boot when the elastic member is preloaded. This eliminates all the slack or voids between the rear spoiler and the lower leg. Any forward movement of the leg will immediately translate to pressure on the front of the ski allowing the skier to easily control the turning of the ski. The hook and loop power strap provided with some ski boots does not produce this effect since it is not possible to obtain an elastic bond with hook and loop fasteners on inelastic straps. In high performance skiing it is desirable to allow this pressure to build up rapidly so a more rigid strap would be desirable. In recreational skiing however it is not necessary or desirable to have such a fast reacting ski, i.e. rigid ski boot. To accomplish this, the instant invention provides the elastic member with an adjusting mechanism to allow less preload of the elastic member thereby allowing more leg travel per given load thereby effectively softening the boot. This is analogous to the super tight steering of a race car compared to that of a common sedan with power steering.
The ski boots used in high performance skiing require fine tuning to maintain the skier's balance. Each person requires a slightly different boot. The skier's physical strength, speed at which the skier skis, the skiers body build and foot/lower leg shape all affect the way a boot works. Ideally boots must be matched to the skier. The instant invention provides and inexpensive means for matching the boot to the skier by changing the physical characteristics of the strap provided by the invention rather than the shell of the boot itself.